1. Field of Invention
This invention relates generally to oil well pumping systems and, more specifically, to a shock absorbing and shock force generating apparatus and method that is intended to reduce stress on the sucker rod and/or other pump components.
2. Background of the Invention
In general terms, an oil well pumping system begins with an above-ground pumping unit, which creates the up and down pumping action that moves the oil (or other substance being pumped) out of the ground and into a flow line, from which the oil is taken to a storage tank or other such structure.
Below ground, a shaft is lined with piping known as “tubing.” Into the tubing is inserted a sucker rod, which is ultimately, indirectly, coupled at its north end to the above-ground pumping unit. Below the sucker rod are located a number of pumping system components, including a standing valve, travelling valve, plunger, and other oil pump components. The sucker rod is typically coupled at its south end to a bushing, which is located north of the valves and plunger.
Oil (or other fluid) is pumped from a hole through a series of “downstrokes” and “upstrokes” of the oil pump, which motion is imparted by the above-ground pumping unit and communicated via the sucker rod. During the upstroke, formation pressure causes a ball located in the standing valve to move upward, allowing the oil to pass through the standing valve and into the barrel of the oil pump. This oil will be held in place between the standing valve and the travelling valve.
On the downstroke, the ball in the travelling valve is lifted off of its seat, to a positive open position, permitting the oil that has passed through the standing valve to pass therethrough. Also during the downstroke, the ball in the standing valve seats, preventing the pumped oil from moving back down into the hole. The force of the up and down motion causes stress on the sucker rod, and over time creates the need to replace this component. A need exists for an apparatus and method that reduces stress on the sucker rod, by creating a shock absorber effect during up and down movement of the pump.
In addition, it is sometimes the case that the pumping system, south of the sucker rod, can become stuck during operation. Typically, this occurs at the mandrel. In such event, it is necessary to remove the stuck portion from the well, so that it may be replaced or repaired. However, it can be difficult to generate the force needed for such removal, and this pulling action can also cause damaging stress to the sucker rod and/or other pump components. Accordingly, a need exists for an apparatus and method that will permit pump removal with less pulling force.
The present invention addresses these needs and provides other, related, advantages.